The invention relates to a device for driving an auxiliary unit, particularly a high-pressure pump wherein a rotatably disposed drive shaft of an internal-combustion engine and a unit shaft of the auxiliary unit are in a mutually operative position by way of a coupling.
Concerning the technical background, reference is made, for example, to German Published Patent Application DE 10 2007 029 651 A1, from which a high-pressure fuel pump arrangement having a pump housing is known for operating a self-igniting internal-combustion engine. This high-pressure fuel pump arrangement has a low-pressure and a high-pressure circulation system and a valve camshaft disposed in a cylinder head of the internal-combustion engine, by which valve camshaft the high-pressure fuel pump arrangement can be driven. The valve camshaft further has a polygonal construction, and components of the high-pressure fuel pump arrangement are advantageously integrated in the cylinder head of the internal-combustion engine.
Furthermore, reference is made to German Published Patent Application DE 10 2008 024 532 A1, on which the present invention is based.
From German Patent Document DE 10 2008 024 532 A1, a device is known for driving an auxiliary unit, particularly a high-pressure pump of an internal-combustion engine. For this purpose, the device has a rotatably disposed driveshaft, preferably a camshaft of the internal-combustion engine. The driveshaft and a unit shaft of the auxiliary unit are in a mutually operative connection by way of a coupling. In a preferred and known manner, this coupling is a jaw coupling.
Such a device of the above-mentioned type for driving an auxiliary unit is, however, acoustically conspicuous, i.e. loud, sensitive to tolerance, expensive, and subject and sensitive to wear in the case of high alternating torques.
It is therefore an object of the present invention to avoid the above-mentioned disadvantages of the known devices.
This and other objects are achieved by a device for driving an auxiliary unit, particularly a high-pressure pump wherein a rotatably disposed drive shaft of an internal-combustion engine and a unit shaft of the auxiliary unit are in a mutually operative position by way of a coupling. The unit shaft has a first bearing on the side facing away from the coupling, and the coupling forms a second bearing for the unit shaft.
The further development according to the invention represents a cost-efficient, acoustically inconspicuous coupling solution that is insensitive to tolerance for connecting, for example, a high-pressure pump camshaft to an existing intake or exhaust camshaft or any other shaft.
In a further development, the coupling consists of a shaft end with an interior profile which engages a complementary shaft end of the unit shaft with an exterior profile. Particularly preferably, the interior profiling and the exterior profiling are polygonal profiles. These further developments are particularly preferred embodiments which can be manufactured in a simple and cost-effective manner and are very advantageous acoustically.
In a further development, at least one of the drive shaft and the unit shaft has at least one cam that generates an alternating torque during operation of the device. The polygonal profile corresponds to the alternating torque. These further development again has a particularly advantageous effect on the acoustic features.
By means of a further development wherein the shaft end with the exterior profile has a circumferential radius in the axial direction, an axial and angular tolerance compensation becomes possible for the unit shaft.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.